This invention relates generally to a process for converting round logs into lumber products, primarily dimension lumber. More particularly, it relates to a log cutting and subsequent rejoining process for converting logs into composite lumber products whereby the yield of lumber from the round wood volume is significantly increased.
In the commonly assigned U.S. Pat. Nos. 3,903,943 and 3,961,654, two cutting and rejoining processes are disclosed that can be utilized for increasing the lumber yield from logs which include certain of the steps employed in the cutting and rejoining process of the present invention. The disclosures in the above-cited issued U.S. Patents are incorporated herein by reference for purposes of providing a complete description and understanding of the present invention.
The centuries-old conversion process of sawing logs into rectangular lumber results in a low yield in that, of the total volume of wood in a log, usually less than half is or can be converted into usable lumber. This is primarily because of the limitation that square or rectangular pieces are cut from a cylindrical log. The actual lumber yields utilizing known processes, of course, vary depending upon a number of factors, such as log diameter and curvature, but even with the best available computer-controlled sawing machines, a normal yield of lumber from an average log is 50% of the total wood volume. With smaller logs the yield is substantially less. The term "lumber" is intended to mean those wood products traditionally having the highest marketable value that are derivable from a longitudinal sawing pattern imposed on a log and which are generally rectangular in cross-section.
The most commonly used log-to-lumber converting process is where saws make a plurality of longitudinal cuts through the log with each successive cut generally being in a plane parallel or perpendicular to an adjacent previous cut. With this process, it is obvious that there are yield limitations simply from the fact that the beginning raw material is cylindrical while the desired final lumber product is rectangular in form. The wood volume not converted into lumber is utilized in a variety of other ways, none of which offer the value of lumber. The sawdust can be used as fuel, particleboard and the like. The solid wood slabs and edgings can be chipped into small pieces suitable for wood pulp production or likewise they can be used for fuel.
In the past, there have been many suggestions of ways to increase the recovery of solid wood products that could be converted from a log. Veneer production and subsequent laminating methods has been one suggestion. In veneer production the cylindrical log is converted into pieces of wood veneer which can then be laminated together to form various wood products such as plywood. Such composite products and their converting processes do convert more of the wood volume into wood products, but they do not have the characteristics of solid sawn lumber.
The aforementioned U.S. Pat. No. 3,961,654 incorporated herein by reference discloses a process and resulting product that can be employed to greatly increase the yield of lumber from cylindrically shaped logs. The process as disclosed is best applied to small logs such as from 5 to 15 inches in diameter. The process described in issued U.S. Pat. No. 3,903,943 is best applied to logs having larger diameters.
Yet another new alternative cutting and rejoining process was conceived from the concept of cutting logs into sector-shaped pieces. The cutting and rejoining process of the present invention results in fewer bonding steps, thereby simplifying the process while still yielding a greatly increased percentage of composite lumber products. It is anticipated that the resulting composite pieces of lumber will have a high value and will be accepted in the marketplace as lumber products.
Accordingly, from the foregoing, one object of the present invention is to convert generally cylindrical logs into composite lumber products whereby the percentage of log volume that is converted to lumber is substantially increased.
A further object is to simplify the process as disclosed in U.S. Pat. No. 3,961,654.
Still a further object is to provide a lumber cutting and rejoining process that yields substantially all flat grained composite lumber.
These and other objects will become more apparent and better understood upon reading the following specification in conjunction with the attached drawing.